Pump operated cooling system using cold fuel

ABSTRACT

A cooling system for an electronics unit of a fuel control which includes a pump with an axial inducer first stage and a centrifugal impeller second stage, the stages being thermally insulated from each other. Relatively cold fuel from a fuel tank enters the axial stage and is delivered from there to a heat exchanger arrangement in the electronics unit. Fuel flow from the heat exchanger is returned to the pump at the inlet of the centrifugal stage which pumps the fuel to the fuel control. A bypass valve, designed to crack at a predetermined pressure, furnishes an additional flow path from the outlet of the axial stage to the inlet of the centrifugal stage.

0 United States Patent 1191 1111 3,733,816 Nash et al. 1 May 22, 1973[54 PUMP OPERATED COOLING SYSTEM 2,970,437 2/1961 Anderson ..60/39.66

USING COLD FUEL FOREIGN PATENTS 0R APPLICATIONS [75] Inventors: John E.Nash, Avon; Charles W.

Grennan, Newington, both of Conn, 567,846 12/1932 Germany ..4l5/179 [73]Assignee: Chandler Evans Inc., West l-lart- Primary Examiner carltoncroyle ford Conn Assistant Examiner-Robert E. Garrett [22] Filed: June11, 1971 Att0rney-Radford W. Luther [21] Appl. No.. 152,264 [57]ABSTRACT 52 U.S. c1 ..60/39.28 R, 60 3966 415/179 A system elewfmm afuel 51 1111. C1. ..F02 9/04,1 026 7/12 whmh mcludes? Pump first 581Field of Search ..415/179, 27,28, stage and a impeller secmd Stage the415 71 143 175 7 144 5 47 80; stages being thermally insulated from eachother. 60/3966 266, 267 Relatively cold fuel from a fuel tank enters theaxial stage and is delivered from there to a heat exchanger 5 ReferencesCited arrangement in the electronics unit. Fuel flow from the heatexchanger is returned to the pump at the inlet UNITED STATES PATENTS ofthe centrifugal stage which pumps the fuel to the 3,507,577 4 1970Swearingen ..415 177 fuel comml- A bypass valve designed crack at2,625,007 1/1953 Truax ..60/39.66 predetermined Pressure, furnishes anadditional flow 3,080,716 3/1963 Cummings et al.. ..60/39.66 path fromthe outlet of the axial stage to the inlet of 2,984,189 5/1961 Jekat..4l5/143 the centrifugal stage. 3,520,133 7/1970 Loft et a1. ..60/39.28R 3,011,313 12/1961 Horton ..60/39.66 7 Claims, 1 Drawing Figure ENGINEPARAMETERS I ELECTRONIC L COMPUTER ELECTROHYDRAULIC FUEL CONTROLMETERING SECTION GAS TURBINE ENGINE PATENTEb I 3,733,816

ENGINE PARAMETERS "L ELECTRONIC I COMPUTER I I-I 30 1 HEAT l IEXCHANGERl 4 l T FUEL I TANK l6 I I I0 I I 56 48 I /TO INLET I I soELECTROHYDRAULIC I- FUEL I I CONTROL 28 I R METERING sEcTIoN I r g 4- IX\\\\ L GAS TURBINE ENGINE INVENTORS JOHN E. NASH ATTORNEY CHARLES WGRENNAN BACKGROUND OF THE INVENTION This invention relates to coolingsystems, and more particularly to cooling systems for electronic unitsmounted on fuel controls.

It is well known that electronic units generate considerable heat, andfrequently require some sort of cooling in order to function properly.In the past, such units have been cooled with engine fuel by arrangementwhich utilized a low temperature fuel and/or a refrigeration cycle. Ingas turbine engine applications, refrigerated fuel may not bepracticable since at least a compressor must be additionally provided.

SUMMARY OF THE INVENTION The invention provides a cooling system for theelectronics unit of an electromechanical fuel control. The coolingsystem forms an integral part of the fuel control itself, therebyobviating the inclusion of a separate system to cool the electronicsunit. A system according to the invention does not require any expansionor compression apparatus, and thus places only a minimum burden upon thepower output of the engine. In addition, a cooling system according tothe invention will not occasion a significant weight increase in thefuel control unit or render it unduly complex.

In brief, the invention employs a pump having two impeller stagesadapted to transfer fuel from a tank to a positive displacement pumpwhich supplies pressur ized fuel to the meteringsection of a fuelcontrol. The first stage preferably embodies an axial inducer to providethe high suction necessary to maintain operation at typical vapor toliquid ratios (V/L) and furnish a limited pressure rise to propel thefuel through the electronics unit. Fuel from the first stage enters aheat exchanger in the electronics unit and passes thence to the inlet ofa centrifugal stage. Fuel from thecentrifugal stage is directed to themetering section via the positive displacement pump which functions as afurther pressure generating source.

The invention is advantageous since the low pressure rise of the firststage yields an extremely small heat input to the fuel from the tank dueto pump inefficiency. For example, a system of the invention can permitoperation of an electronics cold plate at temperatures as low as 165 F,with 135 F fuel inlet temperature at the first stage.

Accordingly, it is a primary object of the invention to provide apump-operated cooling system.

Another object is to provide a cooling system for an electronics unit ofa fuel control for a gas turbine engine.

Still another object is to provide a cooling system incorporating atwo-stage impeller type pump wherein the output flow of the first stageis directed to a heat exchanger, and thence to the inlet of the secondstage.

These and other objects, not specifically recited hereinabove, willbecome more readily apparent from DETAILED DESCRIPTION OF THE PREFERREDEMBODIMENT Referring to the drawing, a fuel control is shown inassociation with a gas turbine engine 2. Fuel from a tank 4 is ducted byappropriate means to the inlet 6 of the fuel control for metering andeventual delivery to the burners of the gas turbine engine 2. Theillustrated fuel control basically comprises a pumping section,generally shown at 8, a metering section 10 which is supplied withpressurized fuel by the pumping section 8, and an electronic computer 12which senses engine parameters such as various speeds, temperatures andpressures, and accordingly controls certain of the elements whichconstitute the metering section such that a properly metered flow isdelivered to the engine. It will be understood that the metering sectionmay also include actuators for control of the variable geometry portionsof the engine.

The pumping section 8 includes a two-stage impeller pump 14 and apositive displacement pump 16, such as a gear pump or vane pump. Theimpeller pump 14 and the gear pump 16 are preferably, although notnecessarily, drivingly interconnected to the engine so as to be operablethereby, and if space limitations warrant, may be interconnected by asingle shaft, thereby minimizing shaft lengths. It will be appreciatedthe interconnection may be of the mechanical (e.g., a gear box),electrical (e.g., an electric motor) or fluid (e.g., hydraulic turthefollowing description taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic view of anembodiment of a cooling system according to the invention.

bine) variety. In order to bypass excess fuel delivered from thepositive displacement pump to the metering section 10, a bypass line(not shown) may be included to interconnect the metering section and theinlet side of the gear pump in any suitable manner.

The impeller pump 14 comprises an inlet conduit 20 which receives inletflow from the tank 4 via inlet 6. Mounted within the inlet conduit is anaxial inducer 22 formed by a hub portion 24 having a rounded end and theusual helical blade 26 carried by the portion 24. The outlet 28 of theaxial inducer communicates with a heat exchanger 30 mounted within theelectronic unit 12 in such a manner as to cool the cold plate thereof,the cooling flow being delivered to the heat exchanger via an inlet duct32 which fluidly communicates with the outlet 28 of the axial inducer22. The flow emerging from the heat exchanger 30, which has absorbedheat from the electronics unit, is delivered to the inlet 34 of acentrifugal impeller pump 36 via an outlet duct 38.

An additional flow path to the inlet 34 of the pump 36 is defined by abypass duct 40 incorporating a by pass valve 42 biased to the closedposition by a spring 44. For high engine flow requirements, bypass valve42 will open upon being subjected to a predetermined pressuredifferential (P P to thereby permit flow from the outlet 28 of the axialinducer to proceed to the inlet 34 of centrifugal impeller 36 throughthe additional path defined by bypass duct 40. The discharge flow in thevolute 46 of the centrifugal impeller 36 is directed to outlet conduit48 from where the flow proceeds to the inlet of the positivedisplacement pump 16.

As shown in the drawing, the axial inducer 22 and the centrifugalimpeller 36 are mounted upon a common drive shaft 52 which extendsthrough the housing 9 and is journaled in a bearing 54. To provide forthe lubrication of the shaft 52, a lubrication line 56 communicates withan annulus recessed upon the bearings cylindrical inner surface. Cleanfluid, which may be filtered fuel,

under pressure, is furnished to the line 56 to insure that contaminantsin the fuel will not deteriorate the engagement between the shaft 52 andthe bearing 54.

Obviously, the effectiveness of the heat transfer operation in theelectronics unit 12 is predicated on delivering relatively cold fuel toinlet duct 32. To this end, the pressure rise across the axial inducermust be kept small (e.g., 5-10 psi) so that the fuel temperature is notsignificantly increased. Furthermore, heat transfer from housing portion9b, which contains heated fuel, to housing portion 9a, which containscold fuel, must be minimized. Thus, a packing of insulating material 58,such as asbestos, is interposed between the housing portions to maintainthe rate of heat transfer at an acceptable level, whereby the heattransfer operation will not be adversely affected.

In operation, the first stage impeller (axial inducer 22) provides thehigh suction specific speed to maintain operation under high V/Lconditions (e.g., 0.45) and the necessary limited pressure rise forpropelling fuel to the heat exchanger. The low pressure rise across theaxial inducer 22 is critical because it inhibits heat rejection to thefuel from pump inefficiency. Flow from the first stage proceeds to theheat exchanger 30 via outlet 28 and inlet duct 32. Heat from theelectronics unit is transferred to the flow leaving heat exchanger viathe units cold plate, the heated flow being directed to the inlet 34 ofthe second stage (centrifugal impeller 36). As the speed and flowincreases in accordance with demands by the engine, the pressuredifferential (P P will accordingly increase. When this differentialattains a predetermined value, bypass valve 42 will open, therebypermitting flow to the inlet 34 of centrifugal inducer 36 to alsoproceed through bypass line 40. Hence, the parallel flow paths to theinlet 34 assure a sufficient pressure rise for charging the inlet ofpump 16. The impeller may operate at relatively high fuel temperatures,such as 250 F, but heat transfer to the fuel discharged by the axialinducer is prevented by the insulation 58. Pressurized flow from pump 16emerges from outlet 50 which directs fuel to metering section 10. Flowmetered by the metering section 10 is directed to the burners of theengine and excess flow delivered to the metering section is returned tothe inlet of the pump 16 by the aforementioned bypass line (not shown).

If centrifugal impeller 36 is sized so as to be capable of supplyingfuel to the engine after starting requirements have been met, the pump16 may include unloading means, such as shown, for example, in US. Pat.application Ser. No. 73,378, filed Sept. 17, 1970, in the names ofCharles W. Grennan and Evert von Moltke and entitled Lifting Tip SealPump.

The illustrated arrangements permit cooling of an electronics unit witha pump having a high V/L suction performance. It has been determinedthat best results are obtainable from the illustrated system when thefirst stage impeller is designed to provide a low pressure rise (i.e.,under 10 psi), and that an axial inducer is the most desirable type ofpump for this application since it inherently yields superior suctionperformance. Moreover, the first stage impeller must be carefullyinsulated from the second stage impeller to frustrate heat conductionbetween the first and second stages.

Obviously, many modifications of the illustrated system are possible inlight of the above teachings. For example, in order to obviate theinsulation 58, the first and second stages of pump 8 could be placed inseparate housings, suitably spaced from each other. It will also beunderstood that the heat exchanger 30 may be associated with a deviceother than an electronics unit for which cooling is desired or, for thatmatter, a plurality of devices.

Hence, the above disclosure is to be considered as being illustrative ofthe invention, and not as being limited thereof, since othermodifications of the described embodiment are possible without departingfrom the spirit and scope of the invention as hereinafter defined by theappended claims.

What we claim is:

L ln combination:

a gas turbine engine;

an electronic computer operatively connected to the engine to sensevarious engine parameters;

a fuel tank adapted to contain fuel for the engine;

. a first impeller pump having an inlet and an outlet for respectivelyreceiving fuel from the tank and discharging fuel;

a second impeller pump having an inlet and an outlet;

a heat exchanger connected to the computer to withdraw heat therefrom,the heat exchanger being fluidly connected to the outlet of the firstimpeller pump to receive a cooling flow therefrom and the inlet of thesecond impeller pump to discharge the flow heated by the computerthereto;

a bypass duct in parallel with the heat exchanger fluidlyinterconnecting the outlet of the first impeller pump and the inlet ofthe second impeller pump to provide an additional flow path from theoutlet of the first impeller pump to the inlet of the second impellerpump;

valve means responsive to a predetermined pressure differential betweenthe outlet of the first impeller pump and the inlet of the secondimpeller pump to control flow in the bypass duct such that a suffi cientpressure rise for charging the inlet of the second impeller pump isassured;

a positive displacement pump having an inlet fluidly connected to theoutlet of the second impeller pump and an outlet for directing apressurized flow to the engine;

means drivingly interconnecting the first impeller pump and the secondimpeller pump; and

means drivingly connecting the first impeller pump,

the second impeller pump and the positive displacement pump to theengine.

2. The combination, as defined in claim 1, wherein the first impellerpump consists essentially of an inducer having a helical blade, andwherein the second impeller pump comprises a centrifugal impeller.

3. The combination, as defined in claim 2, further including:

a metering device operatively connected to the computer so as to becontrolled in accordance with the parameters sensed thereby and to theoutlet of the positive displacement pump for delivering a metered flowof fuel to the engine.

4. The combination, as defined in claim 2, further including:

an insulating material interposed between the first impeller pump andthe second impeller pump to prevent heat transfer therebetween.

5. In combination:

an engine;

a heat generating device for controlling the engine;

a source of fuel for the engine;

a first housing portion having an inlet for receiving fuel from thesource and an outlet for discharging the fuel;

an inducer, having a helical blade, mounted in the first housing portionbetween the inlet and the outlet thereof such that the blade is adaptedto provide a pressure rise at the outlet;

a heat exchanger connected to the device to withdraw heat therefrom, theheat exchanger being fluidly connected to the outlet of the firsthousing portion to receive a flow of cooling fuel;

a second housing portion having an inlet fluidly connected to the heatchanger to receive the fuel heated therein and an outlet for dischargingthe heated fuel;

an impeller mounted in the second housing portion between the inlet andthe outlet thereof for supplying fuel to the engine;

a shaft drivingly interconnecting the inducer and the impeller;

means to drivingly connect the inducer and the impeller to the engine;

an insulating material interposed between the first housing portion andthe second housing portion to prevent heat transfer therebetween;

a bypass duct in parallel with the heat exchanger fluidlyinterconnecting the outlet of the first housing portion and the inlet ofthe second housing portion to provide an additional flow path from theoutlet of the first housing portion to the inlet of the second housingportion; and

valve means responsive to a predetermined pressure differential betweenthe outlet of the first housing portion and the inlet of the secondhousing portion to control flow in the bypass duct such that asufficient pressure rise for charging the inlet of the second housingportion is assured 6. The combination, as defined in claim 5, furtherincluding:

a positive displacement pump having an inlet and an outlet, the inlet ofthe positive displacement pump being fluidly connected to the outlet ofthe second housing portion to receive the output flow thereof;

means drivingly connecting the positive displacement pump to the engine;and

a metering device fluidly connected to the outlet of the positivedisplacement pump to receive a flow of fuel therefrom and fluidlyconnected to the engine to deliver a metered flow of fuel thereto, themetering device being operatively connected to the heat generatingdevice so as to be controlled thereby.

7. The combination, as defined in claim 6, wherein the impeller is acentrifugal impeller, and the inducer is an axial inducer; and whereinthe heat generating device is an electronic computer adapted to sensevarious engine parameters.

1. In combination: a gas turbine engine; an electronic computeroperatively connected to the engine to sense various engine parameters;a fuel tank adapted to contain fuel for the engine; a first impellerpump having an inlet and an outlet for respectively receiving fuel fromthe tank and discharging fuel; a second impeller pump having an inletand an outlet; a heat exchanger connected to the computer to withdrawheat therefrom, the heat exchanger being fluidly connected to the outletof the first impeller pump to receive a cooling flow therefrom and theinlet of the second impeller pump to discharge the flow heated by thecomputer thereto; a bypass duct in parallel with the heat exchangerfluidly interconnecting the outlet of the first impeller pump and theinlet of the second impeller pump to provide an additional flow pathfrom the outlet of the first impeller pump to the inlet of the secondimpeller pump; valve means responsive to a predetermined pressuredifferential between the outlet of the first impeller pump and the inletof the second impeller pump to control flow in the bypass duct such thata sufficient pressure rise for charging the inlet of the second impellerpump is assured; a positive displacement pump having an inlet fluidlyconnected to the outlet of the second impeller pump and an outlet fordirecting a pressurized flow to the engine; means drivinglyinterconnecting the first impeller pump and the second impeller pump;and means drivingly connecting the first impeller pump, the secondimpeller pump and the positive displacement pump to the engine.
 2. Thecombination, as defined in claim 1, wherein the first impeller pumpconsists essentially of an inducer having a helical blade, and whereinthe second impeller pump comprises a centrifugal impeller.
 3. Thecombination, as defined in claim 2, further including: a metering deviceoperatively connected to the computer so as to be controlled inaccordance with the parameters sensed thereby and to the outlet of thepositive displacement pump for delivering a metered flow of fuel to theengine.
 4. The combination, as defined in claim 2, further including: aninsulating material interposed between the first impeller pump and thesecond impeller pump to prevent heat transfer therebetween.
 5. Incombination: an engine; a heat generating device for controlling theengine; a source of fuel for the engine; a first housing portion havingan inlet for receiving fuel from the source and an outlet fordischarging the fuel; an inducer, having a helical blade, mounted in thefirst housing portion between the inlet and the outlet thereof such thatthe blade is adapted to provide a pressure rise at the outlet; a heatexchanger connected to the device to withdraw heat therefrom, the heatexchanger being fluidly connected to the outlet of the first housingportion to receive a flow of cooling fuel; a second housing portionhaving an inlet fluidly connected to the heat changer to receive thefuel heated therein and an outlet for discharging the heated fuel; animpeller mounted in the second housing portion between the inlet and theoutlet thereof for supplying fuel to the engine; a shaft drivinglyinterconnecting the inducer and the impeller; means to drivingly connectthe inducer and the impeller to the engine; an insulating materialinterposed between the first housing portion and the second housingportion to prevent heat transfer therebetween; a bypass duct in parallelwith the heat exchanger fluidly interconnecting the outlet of the firsthousing portion and the inlet of the second housing portion to providean additional flow path from the outlet of the first housing portion tothe inlet of the second housing portion; and valve means responsive to apredetermined pressure differential between the outlet of the firsthousing portion and the inlet of the second housing portion to controlflow in the bypass duct such that a sufficient pressure rise forcharging the inlet of the second housing portion is assured.
 6. Thecombination, as defined in claim 5, further including: a positivedisplacement pump having an inlet and an outlet, the inlet of thepositive displacement pump being fluidly connected to the outlet of thesecond housing portion to receive the output flow thereof; meansdrivingly connecting the positive displacement pump to the engine; and ametering device fluidly connected to the outlet of the positivedisplacement pump to receive a flow of fuel therefrom and fluidlyconnected to the engine to deliver a metered flow of fuel thereto, themetering device being operatively connected to the heat generatingdevice so as to be controlled thereby.
 7. The combination, as defined inclaim 6, wherein the impeller is a centrifugal impeller, and the induceris an axial inducer; and wherein the heat generating device is anelectronic computer adapted to sense various engine parameters.